Introduction:
In the design of distribution substations, the designer needs to consider various components and equipment to ensure efficient and reliable power distribution. One of the key components in the distribution substation is the discrete power tapping, which is used to distribute power to different loads or consumers.

Explanation:
The correct option for discrete power tapping in distribution substations is distributor. Let's understand why:

1. Distributor:
A distributor is a device used in power distribution systems to distribute power to different loads or consumers. It is responsible for dividing the power from a single source into multiple branches or feeders. The distributor can be considered as a network of switches or circuit breakers that control the flow of power to different loads.

2. Power Transformer:
A power transformer is a device used to transfer electrical energy between two or more electrical circuits through electromagnetic induction. It is primarily used for stepping up or stepping down the voltage levels in the power distribution system. While power transformers play a crucial role in substations, they are not directly involved in discrete power tapping.

3. Distribution Transformer:
A distribution transformer is a type of power transformer specifically designed for the distribution of electrical power to consumers at lower voltage levels. It steps down the voltage from the transmission level to the distribution level and provides power to individual consumers or loads. However, distribution transformers are not directly involved in discrete power tapping.

4. Feeder:
A feeder is a conductor or set of conductors used to carry electrical energy from the substation to individual consumers or loads. It can be considered as a distribution line that connects the substation to various distribution points. While feeders are an essential part of power distribution, they are not used for discrete power tapping.

Conclusion:
In the design of distribution substations, the correct option for the discrete power tapping is a distributor. This device is responsible for distributing power to different loads or consumers by dividing the power from a single source into multiple branches or feeders. Power transformers, distribution transformers, and feeders play different roles in the power distribution system but are not directly involved in discrete power tapping.